Various contactless rotary potentiometers have been proposed for providing a linear output response. Contactless potentiometers, of course, are advantageous over resistive type potentiometers because they have a considerably longer lifetime. Although contactless potentiometers which utilize a rotating permanent magnet section and a sensing element were previously known, these proved to have several decided disadvantages; the major disadvantage of such prior devices being that they generally required that the magnet or the sensing element, or both, be formed with a special precalculated shape in order to obtain the desired linearity. This obviously made these potentiometers relatively costly to produce and in addition the shapes required could result in unduly increasing the size of the potentiometers. Examples of such devices are shown in U.S. Pat. No. 3,335,384, issued Aug. 8, 1967 to Herbert Weiss, and in co-pending U.S. Patent Application Ser. No. 613,156 filed Sept. 15, 1975 in the name of Victor M. Bernin, and assigned to the Assignee of the present invention.
The design of the present invention provides excellent linearity in a contactless potentiometer by using cylindrical or rectangular sensing elements and a rotatable permanent magnet segment, which may be merely a segment of a circle with relatively straight sides that pass over said sensing elements and intersect the longitudinal axes of the sensing elements. Thus, the cost of construction of the potentiometer is relatively low. Furthermore, the size of the potentiometer is also maintained relatively small due to the fact that the sensing elements are aligned at an angle and are not spaced in line with each other, as has been proposed for prior contactless potentiometers.
Other notable advantages of the disclosed contactless potentiometer embodiment are that it is highly resistant to shocks and vibrations, which resistive potentiometers are not, and that it is capable of operating up to temperatures as high as 200.degree. C.